This invention relates to an optical axis adjusting mechanism of an optical system for an optical information recording and reproducing device which effects the recording and reproduction of information relative to a storage medium such as an optical magnetic disc, using, for example, a laser beam emitted from a laser diode.
This invention also relates to an optical axis adjusting device for a component part such as an optical pickup for an optical disc device, a compact disc player, an optical video disc player, etc.
This invention relates to an optical axis adjusting method for use in an optical system in an optical data recording and reproducing device in which a laser beam outputted by a laser diode or the like is utilized to record data on a recording medium such as a photo-electro-magnetic disk and reproduce data therefrom, and an optical axis adjusting jig for practicing the method.
In a conventional optical information recording and reproducing device of this type, generally, access to a storage medium is achieved by moving a laser diode and an objective optical system in unison. However, in such an arrangement, since the moving portion is heavy, access time is slow. Therefore, recently there has been developed an optical information recording and reproducing device of the so-called separate type, in which only the objective optical system is moved, while the laser diode remains fixed.
However, in such a separate type of device, the objective optical system is moved along a guide rail. As a result, if the inclination of the optical axis of the laser beam relative to the guide rail deviates even slightly, the deviation of the optical axis of the laser beam from the axis of the objective optical system increases as the objective optical system moves along the guide rail, and the intensity distribution deviates from the center. Further, when the optical axis of the laser beam is displaced with respect to the axis of the objective optical system, the intensity distribution also deviates from the center. Any increase in deviation of the intensity distribution adversely affects a servo signal detection system for detecting a signal for a focusing servo and a tracking servo.
Therefore, in order to avoid such adverse effects on the servo signal detection system, it is necessary to adjust accurately the inclination of the optical axis of the laser beam relative to the guide rail, as well as the displacement of the laser beam relative to the axis of the objective optical system.
Conventionally, the inclination and displacement of the laser beam have been adjusted by moving a laser pen (which comprises a laser diode and a collimator lens integrally connected thereto) or the like, so that the inclination and displacement of the laser beam are adjusted together. As a result, if one of the inclination and the displacement is adjusted, the other is also varied in response thereto. This is disadvantageous, in that accurate adjustment of both the inclination and the displacement is expensive and labor-consuming.
In one example of a known approach, in an optical disc device, a laser beam, irradiated from a light source such as a semiconductor laser, is converged and applied to an optical disc through a predetermined optical system so as to record or reproduce information. In order to effect accurate reproduction of the information, it is necessary to adjust the optical system so that the optical axis of the laser beam can be disposed in a predetermined position.
FIG. 1 shows an example of a mechanism for adjusting the angle of an optical axis of the laser beam, emitted from a source such as a semiconductor laser, for disposing the optical axis of the laser beam in a predetermined position. In this FIG., a mounting base 102, on which a reflecting plate 103 is fixedly mounted, is angularly movable relative to a base plate 101, so that the outgoing angle of the laser beam reflected by the reflecting plate 103 can be adjusted.
FIG. 2 shows an example of a mechanism for adjusting the height of the optical axis (that is, for effecting parallel movement thereof). In this FIG., a mounting base 104, having a prism 105 fixedly mounted thereon, is slidable linearly relative to base plate 101. By adjusting the sliding position of the mounting base 104, the position of the beam incident on an inclined surface of the prism 105 is changed, so that the optical axis of the outgoing laser beam from the prism 105 is moved parallel, thereby adjusting its height.
In an optical disc device, such adjustments of the angle and height of the optical axis must be made both in a direction parallel to the optical disc and in a direction perpendicular thereto. As a result, if separate mechanisms are provided for effecting the adjustments of the angle and height, respectively, it is necessary to provide four such mechanisms, making the construction complicated. Moreover, the adjustments in the two directions are not adequately independent of each other, as mentioned above. As a result, after the adjustments in both directions are completed, fine adjustments must be made in the respective planes, which is disadvantageous in that much time is required for the adjustment.
For this reason, there has been proposed a device in which the adjustment is limited to one direction; however, in this case, the degree of precision of an optical component and its associated mounting components must be improved.
Also, the optical data recording and reproducing device of separation type suffers from the following difficulties: In the device, the part of the objective optical system is moved along a guide rail. Therefore, if the inclination of the optical axis of the laser beam with respect to the guide rail deviates from a predetermined value, then as the part of the object optical system moves, the deviation of the laser beam from the axis of the optical system is increased, so that the distribution of intensity is off-centered. When the distribution of intensity is greatly off-centered, then it will adversely affect a servo signal detecting system for detecting focus servo signals and tracking servo signals.
The tolerance in inclination of the optical axis is extremely small, for instance must 2.degree. or smaller. Therefore, it is considerably difficult to adjust the inclination of the optical axis. Accurate adjustment of the inclination of the optical axis requires lots of time and labor.